This invention constitutes an improvement over the structure and method disclosed in the patent application of Y. K. Pei, Ser. No. 30,859, filed in the U.S. Patent Office on Apr. 22, 1970, which is since abandoned and filed in a continuation-in-part application Ser. No. 146,665 of May 25, 1971, since abandoned, from which a divisional application Ser. No. 250,550 of May 5, 1972, now U.S. Pat. No. 3,871,852, and a continuation application Ser. No. 650,995 of Jan. 21, 1976, respectively, were filed and a further continuation-in-part application Ser. No. 317,559 of Dec. 22, 1972, which is copending herewith, all of which are owned by and assigned to the assignee of the present invention.
In the above-referenced application of Pei, there is disclosed an assembly or matrix of integrally fused tubes useful as a compact regenerative heat exchanger, buoyancy material, sound absorption material, heat insulation material, and the like. The advantages of this type of structure and the requirements for each of the structures of this type, particularly a regenerator structure, are set forth fully in the Pei application and need not be repeated here.
In the above-referenced Pei application, the regenerator structure consists of a plurality of individual, axially parallel, open end glass-ceramic tubes which are thermally bonded to one another and integrated into an overall regenerator structure. Gas flow through the regenerator occurs through the individual tubes, one open end of each tube forming an inlet and the other open end of the tube forming the outlet. In a typical thermal regenerator installation one or both faces of the regenerator is contacted by a seal bar. The regenerator matrix is rotated relative to the seal bar which is urged against the regenerator end surface under an appreciable axial load. Because of matrix end face-seal bar contact under the sealing load, some abrasive wearing of the matrix end face will occur over an extended service period, particularly since the matrix end face is defined by the open ends of the individual tubes. Additionally, the strength of the matrix and its ability to withstand axially or radially applied loads in operation is dependent upon the degree of integral bonding between adjacent tubes. While such matrices made in accordance with the disclosure of the Pei application are capable of functioning satisfactorily as regenerators, and although improvements have been made in increasing the resistance of the matrix end faces to wear, it is desirable to avoid the seal bar wear problems and while maintaining a high level of heat exchange efficiency. Moreover, it is desirable to do away with mechanisms for moving or driving regenerators.
In the above-noted application of Pei, there is also disclosed a heat exchange module which is constructed by superimposing a plurality of layers of tubes, one layer above the other in successive parallel planes, with the tubes in each plane being essentially parallel to each other and transverse to the tubes in at least one of the adjacent layers. The matrix of tubes, each of the tubes having both ends sealed, is heated to soften, expand and fuse the tubes together into an integral module. The sealed ends are opened and a plurality of such modules may be assembled into a toroidally-shaped structure, each module being separated from an adjacent module by a wedge-shape member. In this latter module structure, the problem of seal bar wear has been removed, and there is a crossflow relationship between the two series of passages rather than first passing a hot gas through a tube and then moving the tube to enable passage of a cold gas therethrough to pick up the heat remaining therein from passage of the hot gas therethrough. Although there is no movement of the module in this latter structure, it is still desirable to improve the heat exchange efficiency over that obtained by a crossflow relationship, while retaining the advantages of an integral low expansion glass-ceramic structure of the type described, over the metal or ceramic heat exchange structures of the prior art.
A counterflow recuperator has one of the highest heat exchange efficiencies known to the prior art. However, parallel and counterflow recuperators in high temperature applications made of metals such as nickle alloy are expensive and difficult to shape and braze. Such metal recuperators often leak after repeated cycling. Recuperators have also been made of corrugated sheets of ceramic which are stacked to form a crossflow pattern and then sintered. However, it is difficult to make the joints of these prior art recuperators and failures of recuperators occur in these areas. Heat-resistant materials used in the prior art recuperator bodies are expensive and often fail in thermal fatigue, while sintered ceramic recuperators are sometimes undesirably porous.
Accordingly, it is an object of this invention to provide a recuperator structure having superior properties which utilizes a low expansion, nonporous heat exchange body such as made from glass-ceramic materials, and which does not have the deficiencies of previous regenerator and recuperator structures.
It is another object of this invention to provide an improved method for making a novel recuperator heat exchange assembly.
A still further object of this invention is to provide an improved apparatus, and a method for making such apparatus, for conducting fluids in heat exchange passageways which are substantially parallel to each other and which keep the fluid streams separated, thereby preventing crossflow between different fluid streams.